Ecology Final Exam Review Guide 2024 (Tufts University)

**Final Exam Review Guide** **Bio 142 -- Population/Community Ecology** **Fall 2024 (Richardson, Tufts University)** This guide lists the main concepts/vocabulary on Predation/Herbivory/Parasitism, Community Dynamics and Mutualism. This exam does not require using any equations to solve any speci...

**Final Exam Review Guide** **Bio 142 -- Population/Community Ecology** **Fall 2024 (Richardson, Tufts University)** This guide lists the main concepts/vocabulary on Predation/Herbivory/Parasitism, Community Dynamics and Mutualism. This exam does not require using any equations to solve any specific math type problems. This is not a 100% comprehensive guide, which means you should check all your notes. You do *not* need to know the specific names of individuals mentioned during class or in PowerPoint who are *not* on this list. Finally, remember that any points in the SimUText Ecology text which are in the reading you should know, including examples that support my presentation in class unless stated otherwise (SEE separate list next of what *not* to know in SimUText). **SimUText Reading: you do *not* need to know for the Final Exam:** **For Parasitism, Predation, Herbivory,** - **In section 1, you do not need to know the details of the life cycle of a trematode.** - **In section 4, you do not need to know specific names of function-response curves (type 1, 2, 3) but still need to understand the general relationship of average prey caught vs. prey density and the three basic patterns.** **For Community Dynamics:** - **In section 3, do not need specific hypotheses about food chain length (pg 8)** - **In section 4, do not need to know pg 11, 14-15.** **Parasitism, Predation, Herbivory** Exploitation: - One gains and one loses. Parasites: an organisms that "feeds" off another, needs host alive for at least part of its life cycle - Active transmission: Parasite actively seeks out and invades its host - Requires energy to find and infect - Parasite may have free-living stage - Passive transmission: relies on external factors like vectors, ingestion or environmental contact - Transmission depends on actions of host or vector Ecto parasites: Live outside the host - Externally feed on host body, usually skin or blood - Don't usually deal with immune system - More easily transmitted from host to host - Can be short term or long term Ecto parasite types: - Brood parasites: manipulate the host into raising their young - Birds replace young with their own to be fed and raised - Kleptoparasite: steal resources from host - Social parasites: trick social hosts into accepting them as part of the group - Larvae that trick ants into raising them as their own Endo parasites: Lives inside host - Have to deal with host immune system, selective pressure to get around this - Generally do not kill host bc depend on them as continued feeding source - There is selected pressure for them to not be too virulent - Can have multiple hosts - Can differ throughout life history - May have free living stage where they do not rely on host - Can also be called pathogens if single celled, parasite if multi - Can cause disease in host Endo parasite types: - Microparasites: Multiply directly within a host, usually within a cell - Ex. Diseases - 1/3 of people die from microparasite - Macroparasites: Live in host but releases young outside of hosts body - Ex. Tapeworms, nematodes and flatworms - Parasitoids: Immature stage develops in the hist, typically killing them - Parasitic Flowering plants: - Holoparasite: totally dependent on host plant, cant do photosynthesis - Hemiparasites: Can photosynthesize but lack roots and use host plants nutrient/water - Ex. mistletoe Co-evolution: when a species evolves in response to another species - Diffuse: several species co-evolving - Specific: two species evolving in direct response - parasite/host arms race - A series of reciprocal adaptations - Evolutionary changes in the host due to the parasite modifies the selective environment for the parasite and promotes parasitic evolutionary change which makes the host readapt... Red Queen Hypothesis: It takes all your energy to stay in one place - species evolve just fast enough to stay at the pace of their "enemies" evolution, so they can survive a little longer Sex reproduction: tradeoff between reproduction and immune function - Immune defense takes away energy from repro, idea is that living longer may help reproduce more later - Sexual reproduction was selected for because its high genetic diversity and bc allows host species to evolve new genetic defense against parasites - Red Queen and idea of John Maynard Smith Predation Generalist vs Specialist predators - Generalist: consume wide variety of prey - Flexible diet, can adapt to what's available - Less food scarcity risk but maybe not as efficient hunters - Specialist: focus on one or a narrow range of species - Very adapted/efficient at hunting - More vulnerable to extinction - More tied to cycling of prey Antipredator adaptations: - Chemical: Any type of chemical attack/defense - Venomous bites/stings - Blood from eyes of lizard - Can also be things that make them taste bad or make the poisonous - Aposematism: bright coloration that warn a predator of chemical defenses like poison - Mimicry: a harmless species that appears like something that has a chemical defense so it gets the benefits of aposematism without the cost of the defense - Only works if there are enough of the original non-mimics - Mullerian mimicry: 2 or more chemically defended species that mimic each other, helps reinforce idea and lowers predation for both species - Aggressive Mimicry: predatory camo that helps them hunt and trick prey - Crypsis: coloration like camo that's used to hide from predator - physical/behavioral: shells, spines, escape tools like a tail drop or tricks to make your body look bigger - Predator satiation: synchronized offspring production so overwhelming numbers increase survival odds Offensive Mutualism: - One species aids another in acquiring resources, such as food or nutrients, often by attacking or exploiting a third party, both species benefit - Ex. Hunting dogs and humans Herbivory - Fruit and seeds are high quality while leaves and bark are low quality bc have lots of cellulose that cant be digested by vertebrates - Grazers and browser rely on symbiotic relationship w bacteria in gut that can digest cellulose for them - Grazers: Eat small herbs, grasses and forbs - Browsers: Eat shrubs, tree leaves or bark - Granivores: Eat seeds of plants - Frugivores: Eat plant fruit Anti-herbivory adaptations: - Mechanical: thorns, spines and hairs that deter being eaten - Chemical: toxins or tannins that make them difficult to digest or give bad flavor - Plant defense compounds: chem compounds that coevolved with herbivory - Herbivores can overcome by sniping vascular tissues, eating newer leaves, or evolving digestive enzymes that break down chemicals - Chemical type: Alkaloids, Phenolics, Terpenoids, Capsaicin: burning sensation effecting mammals but not birds - Nutritional: Try to be les nutritious than your neighbor - Grow less nitrogen and phosphorus but more cellulose (hard to digest) - Tannins prevent digestion of nitrogen (both chem and nutritional) - Tolerance: evolved to regrow tissues quickly after being eaten - Common in grasslands/meadows - Humans blocking grazing for these species can lead to slower growth Co-evolution: predator/prey arms race: - Encounter term: the rate at which predators and prey encounter each other - Depend on population density and environment - Search efficiency: For every encounter that occurs, how well can the predator get the prey - Depend on predators and prey abilities - Conversive factor: The efficiency they prey energy is used/converted for predator - Thought to be 0.1 or 10% - Know what the terms of each of the predator/prey equations mean and the basic relationship of each term to each other (but you will *not* need to solve for anything mathematically) - Predator population growth based on prey: - dNpredator/dt = abNpreyNpredator -- mNpredator - Prey population growth w predator influence - dNprey/dt = rpreyNprey -- aNpredatorNprey - a = search efficiency - b = conversion factor (0.1) - NpreyNpredator = encounter term - m = predator mortality - dN(prey/predator)/dt = normal pop growth - N = population - R = growth rate Recognize typical cycling pattern of predator/prey interactions - Coupled oscillations - Earliest studied cycle is lynx and hare - Cycle together but slightly offset, a lag for the predator population - Predator peaks just after prey peaks Lotka-Volterra equations for prey/predator growth Example of snow/moose/wolf/fir tree interactions - Wolf population increases when the eat more moose, decreasing the moose population and increasing fir tree growth - Can be effected by environmental variation - Lots of snow makes it harder for moose to escape wolves and increase their search efficiency Three types of predator functional responses - Handling time: the amount of time it takes to capture, eat and digest a prey item - Determines a predators feeding efficiency and prey type - Type 1: Linear response, Lotka-Volterra - Predators eat prey in direct proportion to the preys abundance - Uncommon because most predators have a handling time\\ - Ex. Lynx and hares - Type 2: Logistic response - As prey abundance increases, so does predation rate until there are too many and the catch rate plateaus - More common in nature because it takes handling time into consideration - Ex. Otters - Type 3: - Some predators only focus on prey when it becomes more abundant - Seals feed more on salmon when they are present in large numbers Invasive vs native predators/parasites - Introduced predators have a larger impact on native species than native ones - Species had adapted to respond to native predators but not introduced ones - Ex. Snake introduced to Guam killed off all bird species - Introduced parasites are also more harmful than native because they aren't adapted to respond - Ex. US chestnut tree, Serengeti national park lions - Parasites as biocontrol of invasives - Usually more host specific than a predator so less risk of large unexpected consequence - Ex. Parasite flies limit fire ant population - Ex of predator: Cane toads brought to control smth but now overrun Australia Human Predation: the most harmful but we are trying to put in limits to control the effect on prey populations - Hunting and fishing has devastated prey populations like cod Overkill Hypothesis: Humans migrated and hunted megafauna to extinction easily because they were not adapted to us - Evidence: sudden extinctions that followed the spread of humans - Species hunted by humans show rapid evolution to smaller size and younger reproduction bc our hunting preference for large mammals - African megafauna survived bc they adapted to humans as we evolved there - Extensive archeological evidence of large mammal hunting Megafauna extinctions: - NA used to have mammoths, giant sloths, giant beavers, saber tooth, lions etc - They all died out or became non-mega while others stayed in places like Africa - Two factors: Overkill and climate change, both true - Climate: changes during the ice ages reduced living space and food supply **Community Dynamics** **Ecological** **Community: The association of all species in a given area** - **Community dynamics studies the nature of these interactions and how the influence community structure** Early, mid and late successional stages - Early: 0-10 years - Dominated by high repro and fast growing plants like herbs, grasses and annuals - Stage has high sunlight and good dispersal - Middle: 10-50 years - Dominated by trees - Stage has restoration of canopy cover and beginning of slower growing dominant species like trees - Late: 50-100+ years - Trees are dom biomass - Lower tree density than middle bc the strongest competitors outcompete neighbors Disturbance: An abiotic event that changes the survival rate of 1+ species - Can open up resources and space fr some species - Can vary by frequency and magnitude - Small impact disturbances are the most common - Primary vs secondary succession - Primary: After a disturbance that removes all organisms and exposes bare substrate - Starting from scratch - Ex. Fires, volcanoes, glaciers, floods - Leaves nutrient poor soil and relies on primary/pioneer species to make habitable for rest of community - Secondary: After a disturbance where some organisms survive - Still needs nutrient balancing and different stages of succession but not starting from scratch - Ex. Abandoned agriculture fields - Primary species vs climax species - Primary/pioneer species: - Can tolerate harsh abiotic conditions, grow and reproduce quickly - Modify the environment to make more habitable for other species - Ex. Colonizing plants with nitrogen fixing bacteria in the roots - Early successional species - Good dispersers with fast growth in high sunlight - High productivity with simple food webs - Climax species: - Final stable species in the mature enviro - Slower growth with less dispersal, good competitors for nutrients and light Succession Models: Facilitation, Inhibition, Tolerance - Facilitation: Early species modify the envrio to facilitate colonization by less tolerant species - They improve soil quality, reduce the pH and provide shade - Only the early successional species can establish - Common in primary succession but can also happen in secondary - Inhibition: All species have potential to survive at the site, but those that arrive quickest inhibit the growth of later species - As the short-lived colonizers die quickly, succession slowly proceeds to longer lived species - More common in secondary succession - Tolerance: All species have potential to survive in unoccupied site, the late successional species arrive later/grow more slowly but will outcompete them eventually - Early species have no impact on later species Intermediate disturbance hypothesis: Intermediate levels of disturbance promote the best diversity - Sousa study: Found that medium intertidal boulder (intermediate amount of disturbance) had the most species/diversity - Compare to low (large) and high (small) disturbance boulders - Joeseph Connell: "disturbances promote coexistence between colonizing and dominating species" Food chain: How organic matter like energy/nutrients moves through a community - Food web is used to connect multiple food chains and trophic levels Trophic level: A position in a food chain - Primary producers: Use sunlight to make energy/organic compounds - Primary consumers: Consume producers (herbivores) - Secondary/tertiary consumers: Consume lower level consumers (predators) Top down and bottom-up control: - Top-down: Top trophic levels limit size of the levels they consume - Population control through predation - More important in complex/stable ecosystems - May be more at play overall - Ecology of fear: fear of predation can influence foraging behavior of lower trophic species, effects interactions as a behavioral cascade - Trophic cascade: adding/removing important predator species can affect the whole food chain - Ex. Wolves or sea otters - Bottom-up: Lower trophic species will affect higher trophic species by limiting resource availability - More important in simple/disturbed ecosystems that might not support top predators - Ex. Nitrogen limitation: plant biomass is dependent on nitrogen, primary consumer pop is dependent on plants... - Ex. Leaf litter: the amount of leaf litter entering a stream control litter consumers and their predators - Ex. Eutrophication: excess nutrients causes algal bloom that lowers water oxygen levels - Both are very important and always at work within a community - Even so, top down seems to have a greater effect on food web than bottom up for a given ecosystem - Environmental stress hypothesis - How diversity/stress might favor top down or bottom-up control - Different species are impacted by types of control differently - Some have higher mortality from nutrient access, some have higher from predation Indispensable mortality: The proportion of deaths in a population that are unavoidable and would occur regardless of other mortality factors. - Usually intrinsic causes like aging and genetic factors, or unavoidable environmental conditions - The amount of mortality from one factor that would not be replaced by another - Small changes in deaths in one part of life cycle doesn't really effect population? Community Stability: - Function of an ecosystem remains relatively constant over time or can recover from disturbances - Persistence; the ability of a community to stay roughly the same over time - Communities are not static, they are in a constant flux due to the forces of disturbance and succession - Previously were thought to be at a stable equilibrium Resistance and resilience - Resistance: The ability to tolerate a disturbance - Can change by disturbance type - Assessed right after disturbance - Resilience: The ability to recover from a disturbance and return to pre-disturbance state - Return time: amount of time until a community stops changing post disturbance - Needs time to pass before being assessed - Ex. Coral bleaching - Low resistance: can be destroyed by temp increases and pH changes - Bleaching of algae and weakened calcification - We can promote resistance: spreading heat resistant strain of coral - We can promote resilience: intentional cooling, pH adjustments, or coral transplants Why does diversity increase stability? - Tilman: Increases diversity stabilizes the community because they are more likely to have disturbance-tolerant species - These species can compensate for less tolerant species in the event of a disturbance, helping increase the communities resistance - Large plant diversity limits the effects of weather flux on plant biomass - More consistent year by year - The higher the diversity, the better a community can resist invasive species Alternative stable states: Sometime more than one stable community can exist in a given enviro - Ex. Yellowstone w and without wolves were two different but stable communities - Can be demonstrated by removal of key species, but reintro wont always make community go back to original stable state - Removal of spider than force herbivore insects to rely on common dominant species led to decrease in plant species richness bc insects fed more widely - Re-intro did not restore plant diversity, the new stable community remained Ecosystem engineers (know examples) - Physically modify a habitat and alter resources for other species - Can be keystone species but not always - Autogenic: Directly transform living/nonliving matter - Behavior modifies the habitat - Ex. Beavers, termites - Allogenic: Change the enviro due to their own physical structure - Ex. Trees, coral reefs Dominant species vs Keystone Species - Dominant: Species with high relative biomass - Still negatively effect ecosystem if they leave, but not more than predicted - Keystone: Have much bigger impact on the community than predicated by their relative biomass - Usually identified by looking at the effect of their removal on community - Invasive species are not included - Ex. Sharks, wolves, otters, beavers How to measure community importance (CI) - Community Importance: The change in a community that results from a change in a given species' abundance - - t~N~ = total biomass in the intact community (before removal) - t~D~ = total biomass in the community when species *i* has been removed - p~i~ = proportional biomass of species *i* before removal - Keystone species = CI \>\> 1 **Mutualism** **Symbiosis:** - **Mutualism: Interactions in which both species benefit** - **Commensalism: interactions in which one species benefits and the other is not helped or harmed** - **Parasitism: Interactions in which one species benefits and the other is harmed** **Co-evolution: two or more species reciprocally affect each others evolution** - **Direct each others evolution through their interactions** - **Basis for mutualism evolving between species** **Obligate vs Facultative mutualism** - **Obligate: Neither species can survive without the other** - **Ex. Leafcutter ants and the fungus they farm** - **Facultative: They can survive independently but do better together** - **Ex. Ants and aphids** **Mutualism types: Dispersive, defensive and resource-based** **Dispersive mutualism: One species helps disperse the seeds or pollen of another species, and in return, it receives a benefit, typically food** - **Three important components for pollination** - **An attractant/reward to entice a pollinator** - **Behavior that ensures pollinators will visit more than one plant** - **Pollinator has anatomical feature that allows it to carry pollen** - **Pollinator: Bees, birds and bats** - **Bees: rewards of pollen (protein) and nectar (carbs)** - **Travel from flower to flower in large area, usually same species (floral constancy)** - **Hairs and pollen pouches to carry pollen** - **See UV patterns on flower to attract them** - **Other ex.** - **Hummingbirds that are attracted to red, need lots of nectar** - **Moths that are attracted to pale color and smell** - **Flies that are attracted to carrion smell** - **Plants are better off with specialist pollinators (coevolved to pollinate one specific species) bc more efficient pollen delivery** - **Pollinators are better off with generalist bc they can go to more than one plant for food source** - **Pollinator syndrome: plant species with common pollinators have common features** - **Seed dispersers: Birds, mammals (bats), and fish (piranhas)** - **Birds: get vitamins and sugars from the fruits** - **Seeds pass through gut and get prepared for germination before dispersal** - **Fruits are more costly to produce compared to wind dispersal, so why?** - **Leads to wider dispersal which means can colonize new area and also less nearby competition** - **Avoids seed predators** - **Allows for direct dispersal into optimal sites** **Defensive mutualism: One species protects another in return for a reward like food or shelter** - **Ex. Amazonian devils are a species of plant that rely on ants to inhibit the growth of other plants nearby in return for eating plant?** **Resource-based mutualism: Two species can better obtain resources together** - **Ex. Mycorrihzal fungi in roots supply phosphorous and the plant supplies carbs** **Human/Domesticated animals** - **Example of both defensive and resource-based mutualism** - **Facultative leaning because both can survive without each other typically** **Equations:** **There are *no* specific equations you need to know to solve any math type problem.**